error[E0005]: refutable pattern in local binding
  --> $DIR/issue-31561.rs:8:9
   |
LL |     let Thing::Foo(y) = Thing::Foo(1);
   |         ^^^^^^^^^^^^^ patterns `Thing::Bar` and `Thing::Baz` not covered
   |
   = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
   = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
note: `Thing` defined here
  --> $DIR/issue-31561.rs:1:6
   |
LL | enum Thing {
   |      ^^^^^
LL |     Foo(u8),
LL |     Bar,
   |     --- not covered
LL |     Baz
   |     --- not covered
   = note: the matched value is of type `Thing`
help: you might want to use `if let` to ignore the variants that aren't matched
   |
LL |     let y = if let Thing::Foo(y) = Thing::Foo(1) { y } else { todo!() };
   |     ++++++++++                                   ++++++++++++++++++++++
help: alternatively, you might want to use `let else` to handle the variants that aren't matched
   |
LL |     let Thing::Foo(y) = Thing::Foo(1) else { todo!() };
   |                                       ++++++++++++++++

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.